(a) An agreement under this subchapter supersedes a previous statute concerning wages, salaries, rates of pay, hours of work, or other terms and conditions of employment to the extent of any conflict with the statute.
(b) An agreement under this subchapter preempts any contrary statute, executive order, local ordinance, or rule adopted by the state or a political subdivision or agent of the state, including a personnel board, a civil service commission, or a home-rule municipality.

(c) An agreement under this subchapter may not diminish or qualify any right, benefit, or privilege of an employee under this chapter or other law unless approved by a majority vote by secret ballot of the members of the association recognized as a sole and exclusive bargaining agent.